Water contamination is a serious problem in the United States and throughout the world. In the last several decades water pollution has been the subject of increased government scrutiny and regulation. In response to the need for clean drinking water and the need to maintain clean water in rivers, lakes, oceans, and wet lands, detailed statutory and regulatory schemes have been developed at the state and local levels in the United States. These statutory and regulatory schemes relate to many types of activities that can produce water pollution. Such activities include everything from controlling and monitoring the quality of run-off from farming operations and in storm drainage systems, to the regulation of industrial, mining, and commercial activities such as oil and gas exploration. Almost any activity that produces or has the capability of producing significant quantities of tainted water will likely be regulated by state and federal regulations. Several regulatory agencies deal extensively with the regulation of water emissions. Some of these agencies include the United States Environmental Protection Agency (EPA), which has broad regulatory authority; the United States Coast Guard, which regulates the use of navigable waters; state Oil and Gas Boards, which regulate produced waters at well sites; and state and federal agencies dealing with mine regulation.
Various water contaminants, and specific activities that have the capability of producing water contamination, are the subject of water quality regulations. Materials that may be regulated range from pesticides and fertilizers to petrochemical-related hydrocarbons and numerous chemicals and hazardous materials. Any materials that may arguably be detrimental if placed in the water supplies of the nation are subject to regulation and controlled emission.
Heavy metals are one class of water contaminant that is encountered widely in the environment. Essentially all transition metals can exist as dissolved ions in water. Examples of heavy metals that may become water contaminants include lead, manganese, cobalt, cadmium, and others. These materials present significant water contamination problems when they exist in a stream or water supply. Consuming water that contains heavy metals can be detrimental to the health of humans and animals alike. Heavy metal poisoning can be a serious public health issue. Accordingly, there is significant interest in extracting heavy metals from water supplies.
At the same time, removal of heavy metals from water in bulk is a difficult and expensive process. While the chemistry of heavy metals is well understood, applying that chemistry to remove heavy metals from water in the environment and at ambient conditions has proven difficult and expensive. These processes often require large bulky processing facilities and can produce waste products that are themselves hazardous and pose difficult disposal issues.
Adding to the problem is that fact that some old industrial and mining operations have produced heavy metal emissions over many decades and in some cases for more than a century. Many of these operations pre-date modern water contamination control regulation and the development of modern water contamination control technology. Thus, these operations produced heavy metal emissions with not much effort directed to removal of the metals from the water or limitation of the contaminants prior to their release into the environment.
Where these types of facilities have continued in operation, they have been brought up to standards by the application of the necessary modifications as required by the regulatory schemes mentioned above. However, in cases where mines and other industrial facilities closed down prior to the implementation of contamination control systems and technology and the implementation of modem regulatory schemes, it is quite possible for such facilities to continue to produce water emissions tainted by heavy metals.
This is particularly true of mining operations where ground water flows through the mine and exits into local streams and drinking water. Heavy metal contamination of natural water sources continues to be a problem in the mining communities long after mining has ceased. Due to the undesirability of heavy metal contamination in the water, much effort and expense is necessary to remediate these problems, often with less than adequate results.
Many problems exist with traditional heavy metal or water treatment remediation methods. One such method is metal hydroxide precipitation to remove heavy metals. This method, and many other conventional methods, adds large quantities of chemicals to the waste stream that might contain quantities of contaminants at levels less than parts per thousand. These types of procedures can result in large quantities of metal-contaminated or metal-containing precipitate. As mentioned above, the disposal of the resultant metal-laden precipitate presents disposal problems of its own, particularly if the precipitate has the potential to later leach metals back into the environment.
Most conventional processes for water remediation require complex and bulky equipment. These processes are expensive and sometimes result in less than adequate cleaning of the water. Conventional processes often result in a waste material that itself is hazardous and must be disposed of using expensive techniques that may be the subject of further regulations.
Further, the ability to extract contaminants from water creates the potential of both sensing and monitoring the levels of those contaminants in a given water sample.
Thus, there is a need to provide improved methods and apparatus for extracting contaminants from water. More particularly, there is a need to provide methods and systems that are capable of quantifying and/or extracting metal contaminants, e.g., heavy metals, from water.